Delphic Expanse

The Delphic Expanse was an area of space in the Alpha Quadrant approximately 50 light years from the Sol system. While its exact dimensions remain unknown, during the 22nd century, Vulcan scientists estimated it to be around 2,000 light years across. The Delphic Expanse was a vast region of space, home to numerous species. (ENTepisode: "The Expanse")

Entering and exiting the Expanse was extremely hazardous due to thermobaric clouds which surrounded the area. Travel through the Expanse was further complicated by numerous subspace anomalies which littered the area at random; these anomalies were responsible for numerous inexplicable events.

During the 2130s, for instance, a Klingon vessel emerged from the Expanse and with its crew anatomically inverted, but still alive. These anomalies often led species from outside of the Expanse to ban entry and exit. (ENTnovelization: The Expanse).

In late 2152, the Vulcan vessel Seleya was drawn into the Expanse and all contact was lost. The Vulcan's dispatched the Vaankara to investigate, but contact was also lost with this vessel. It was later discovered that the crew had gone insane within two days of entering the Expanse. (ENTepisode: "The Expanse"; ENTepisode: "Impulse")

The Xindi attack of 2153 on Earth was launched from the Delphic Expanse in March of that year. The attack, which left seven million Humans dead, prompted United Earth to dispatch the starship Enterprise (NX-01) to enter the Expanse and search for the Xindi to stop them from launching a second, devastating attack on Earth and thwart their genocidal plans for the Human race.

On this mission, the crew of Enterprise (NX-01) discovered an expansive system of ancient Spheres that covered much of the Delphic Expanse. These Spheres, it was discovered, were responsible for the spatial anomalies that roamed the Expanse, and were in fact responsible for the existence of the Delphic Expanse itself. (ENTepisode: "Anomaly")

The Delphic Expanse had been created by an extra-dimensional race of beings from the 26th century known as the Sphere Builders. The Sphere Builders, known to the Triannons as the Makers and to the Xindi as the Guardians, had traveled back to the 12th century to create the Spheres after their attempted invasion of the Milky Way Galaxy was thwarted by the United Federation of Planets in their 26th century; the Spheres were designed to gradually grow and transform space so as to make it habitable for the Sphere Builders. The Expanse had been growing for 1,000 years prior to the Xindi attack on Earth, and would eventually grow to encompass the entire galaxy as part of their invasion plans. The attack on Earth itself had been prompted by the Sphere Builders as part of an attempt to retroactively prevent the Federation from forming. (ENTepisode: "Zero Hour")

The Delphic Expanse ceased to exist when the space within the Expanse was restored to its natural state in January of 2154. Enterprise (NX-01) destroyed Sphere 41, an important link in the Sphere network. The destruction of this Sphere caused a chain reaction, destroying the others and removing the source of the spatial anomalies that had plagued the Expanse for centuries. (ENTepisode: "Zero Hour")

The location of the Delphic Expanse in relation to the known astropolitical scene of the Alpha and Beta Quadrants of the 23rd and 24th centuries is unclear at best. Some have theorized that the Delphic Expanse may have been located in the area of space that included Ferenginar and Cardassia Prime, to explain why it is that these two races, already space-faring by the time of the 22nd century, remained unknown to the Federation until the 24th century; presumably, the Federation would have kept some distance away from the area of the former Delphic Expanse following the Xindi Crisis, expanding instead towards Romulan and Klingon space until the late 23rd or early 24th centuries. Star Charts, while written prior to the third season of Star Trek: Enterprise, depicts the Cardassian Union, Ferengi Alliance, Tzenkethi Coalition, and Breen Confederacy as being roughly fifty light years from Earth; this supports the hypothesis that those planets are found in the area of the former Delphic Expanse.